Merge for the 1.68.0 beta

doc/algorithm.qbk

@@ -64,6 +64,8 @@ Thanks to all the people who have reviewed this library and made suggestions for
 
 [section:Misc Other Algorithms]
 [include clamp-hpp.qbk]
+[include find_not.qbk]
+[include find_backward.qbk]
 [include gather.qbk]
 [include hex.qbk]
 [include is_palindrome.qbk]

doc/find_backward.qbk

@@ -0,0 +1,116 @@
+[/ File find_backward.qbk]
+
+[section:find_backward find_backward ]
+
+[/license
+Copyright (c) 2018 T. Zachary Laine
+
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+]
+
+The header file 'find_backward.hpp' contains variants of the stl algorithm
+`find`. These variants are like `find`, except that the evaluate the elements
+of the given sequence in reverse order.
+
+Consider how finding the last element that is equal to `x` in a range is
+typically done:
+
+    // Assume a valid range if elements delimited by [first, last).
+    while (last-- != first) {
+        if (*last == x) {
+            // Use last here...
+        }
+    }
+
+Raw loops are icky though.  Perhaps we should do a bit of extra work to allow
+the use of `std::find()`:
+
+    auto rfirst = std::make_reverse_iterator(last);
+    auto rlast = std::make_reverse_iterator(first);
+    auto it = std::find(rfirst, rlast);
+    // Use it here...
+
+That seems nicer in that there is no raw loop, but it has two major drawbacks.
+First, it requires an unpleasant amount of typing.  Second, it is less
+efficient than forward-iterator `find` , since `std::reverse_iterator` calls
+its base-iterator's `operator--()` in most of its member functions before
+doing the work that the member function requires.
+
+[heading interface]
+
+    template<typename BidiIter, typename T>
+    BidiIter find_backward(BidiIter first, BidiIter last, const T & x);
+
+    template<typename Range, typename T>
+    boost::range_iterator<Range> find_backward(Range & range, const T & x);
+
+These overloads of `find_backward` return an iterator to the last element that
+is equal to `x` in `[first, last)` or `r`, respectively.
+
+    template<typename BidiIter, typename T>
+    BidiIter find_not_backward(BidiIter first, BidiIter last, const T & x);
+
+    template<typename Range, typename T>
+    boost::range_iterator<Range> find_not_backward(Range & range, const T & x);
+
+These overloads of `find_not_backward` return an iterator to the last element
+that is not equal to `x` in `[first, last)` or `r`, respectively.
+
+    template<typename BidiIter, typename Pred>
+    BidiIter find_if_backward(BidiIter first, BidiIter last, Pred p);
+
+    template<typename Range, typename Pred>
+    boost::range_iterator<Range> find_if_backward(Range & range, Pred p);
+
+These overloads of `find_if_backward` return an iterator to the last element
+for which `pred` returns `true` in `[first, last)` or `r`, respectively.
+
+    template<typename BidiIter, typename Pred>
+    BidiIter find_if_not_backward(BidiIter first, BidiIter last, Pred p);
+
+    template<typename Range, typename Pred>
+    boost::range_iterator<Range> find_if_not_backward(Range & range, Pred p);
+
+These overloads of `find_if_not_backward` return an iterator to the last
+element for which `pred` returns `false` in `[first, last)` or `r`,
+respectively.
+
+[heading Examples]
+
+Given the container `c1` containing `{ 2, 1, 2 }`, then
+
+    find_backward        ( c1.begin(), c1.end(), 2                          ) --> --c1.end()
+    find_backward        ( c1.begin(), c1.end(), 3                          ) --> c1.end()
+    find_if_backward     ( c1.begin(), c1.end(), [](int i) {return i == 2;} ) --> --c1.end()
+    find_if_backward     ( c1.begin(), c1.end(), [](int i) {return i == 3;} ) --> c1.end()
+    find_not_backward    ( c1.begin(), c1.end(), 2                          ) --> std::prev(c1.end(), 2)
+    find_not_backward    ( c1.begin(), c1.end(), 1                          ) --> c1.end()
+    find_if_not_backward ( c1.begin(), c1.end(), [](int i) {return i == 2;} ) --> std::prev(c1.end(), 2)
+    find_if_not_backward ( c1.begin(), c1.end(), [](int i) {return i == 1;} ) --> c1.end()
+
+[heading Iterator Requirements]
+
+All variants work on bidirectional iterators.
+
+[heading Complexity]
+
+Linear.
+
+[heading Exception Safety]
+
+All of the variants take their parameters by value and do not depend upon any
+global state. Therefore, all the routines in this file provide the strong
+exception guarantee.
+
+[heading Notes]
+
+All variants are `constexpr` in C++14 or later.
+
+[endsect]
+
+[/ File equal.qbk
+Copyright 2018 T. Zachary Laine
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt).
+]

doc/find_not.qbk

@@ -0,0 +1,83 @@
+[/ File find_not.qbk]
+
+[section:find_not find_not ]
+
+[/license
+Copyright (c) 2018 T. Zachary Laine
+
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+]
+
+The header file 'find_not.hpp' contains a variants of a the stl algorithm
+`find`. The algorithm finds the first value in the given sequence that is not
+equal to the given value.
+
+Consider this use of `find()`:
+
+    auto std::vector<int> vec = { 1, 1, 2 };
+    auto it = std::find(vec.begin(), vec.end(), 1);
+
+This gives us the first occurance of `1` in `vec`.  What if we want to find
+the first occurrance of any number besides `1` in `vec`?  We have to write an
+unfortunate amount of code:
+
+    auto std::vector<int> vec = { 1, 1, 2 };
+    auto it = std::find_if(vec.begin(), vec.end(), [](int i) { return i != 1; });
+
+With `find_not()` the code gets much more terse:
+
+    auto std::vector<int> vec = { 1, 1, 2 };
+    auto it = find_not(vec.begin(), vec.end(), 1);
+
+The existing `find` variants are: `find()`, `find_if()`, and `find_if_not()`.
+It seems natural to also have `find_not()`, for the very reason that we have
+`find_if_not()` -- to avoid having to write a lambda to wrap the negation of
+the find condition.
+
+[heading interface]
+
+    template<typename InputIter, typename Sentinel, typename T>        
+    InputIter find_not(InputIter first, Sentinel last, const T & x);
+
+    template<typename Range, typename T>
+    boost::range_iterator<Range> find_not(Range & r, const T & x);
+
+These overloads of `find_not` return the first value that is not equal to `x`
+in the sequence `[first, last)` or `r`, respectively.
+
+[heading Examples]
+
+Given the container `c1` containing `{ 0, 1, 2 }`,  then
+
+    find_not ( c1.begin(),     c1.end(),    1 ) --> c1.begin()
+    find_not ( c1.begin(),     c1.end(),    0 ) --> std::next(c1.begin())
+
+[heading Iterator Requirements]
+
+`find_not` works on all iterators except output iterators.
+
+The template parameter `Sentinel` is allowed to be different from `InputIter`,
+or they may be the same.  For an `InputIter` `it` and a `Sentinel` `end`, `it
+== end` and `it != end` must be well-formed expressions.
+
+[heading Complexity]
+
+Linear.
+
+[heading Exception Safety]
+
+`find_not` takes its parameters by value and do not depend upon any global
+state. Therefore, it provides the strong exception guarantee.
+
+[heading Notes]
+
+`constexpr` in C++14 or later.
+
+[endsect]
+
+[/ File equal.qbk
+Copyright 2018 T. Zachary Laine
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt).
+]